I’m updating several of my Web Configuration utilities for various applications that provide post-installers or tools to otherwise set up Web sites. With Vista rolling around being able to select an application pool to assign the site to is becoming more important because in IIS7 the Application Pool determines the .NET version that is used as well as the pipeline mode (classic or the new integrated mode). So for setting up ASP.NET 2.0 applications typically you’ll want to select a classic pipeline application pool for the application so you can get easy debugging (debugging integrated mode with VS takes a little more work).

I’m updating this stuff specifically for my West Wind Web Store configuration utility as well as a standalone tool the Web Configuration Tool both of which need this functionality. Here’s what the Web Site Configuration Tool looks like:

In this case it’s using IIS 7 so the .NET version isn’t selectable as it’s selected as part of the Application Pool. For IIS 6 both .NET version and App Pool are available for IIS 5 only the .NET version is available.

So how do you get the ApplicationPools available, select and set one and create a new one? There are actually a number of ways (especially with IIS7) but the most widely supported by recent versions of IIS is still by using ADSI and DirectoryServices in .NET.

I talked about using ADSI for IIS with .NET a long while back with some examples of how to get virtuals and set properties etc. there.

So, here’s some additional code to deal with Application Pools in my WebConfiguration class (note there are a few depencies in this code, but you should be able to glean the general idea):

/// <summary>

/// Returns a list of all the Application Pools configured

/// </summary>

/// <returns></returns>

public ApplicationPool[] GetApplicationPools()

{           

    if (ServerType != WebServerTypes.IIS6 &&

        ServerType != WebServerTypes.IIS7)

        return null;

    DirectoryEntry root = this.GetDirectoryEntry("IIS://" + this.DomainName + "/W3SVC/AppPools");

      if (root == null)

            return null;

    List<ApplicationPool> Pools = new List<ApplicationPool>();

    foreach (DirectoryEntry Entry in root.Children)

    {

        PropertyCollection Properties = Entry.Properties;

        ApplicationPool Pool = new ApplicationPool();

        Pool.Name = Entry.Name;

        Pools.Add(Pool);

    }

    return Pools.ToArray();

}

/// <summary>

/// Create a new Application Pool and return an instance of the entry

/// </summary>

/// <param name="AppPoolName"></param>

/// <returns></returns>

public DirectoryEntry CreateApplicationPool(string AppPoolName)

{

    if (this.ServerType != WebServerTypes.IIS6 &&

        this.ServerType != WebServerTypes.IIS7)

        return null;

    DirectoryEntry root = this.GetDirectoryEntry("IIS://" + this.DomainName + "/W3SVC/AppPools");

    if (root == null)

        return null;

    DirectoryEntry AppPool = root.Invoke("Create","IIsApplicationPool",AppPoolName) as DirectoryEntry;           

    AppPool.CommitChanges();

    return AppPool;

}

/// <summary>

/// Returns an instance of an Application Pool

/// </summary>

/// <param name="AppPoolName"></param>

/// <returns></returns>

public DirectoryEntry GetApplicationPool(string AppPoolName)

{

    DirectoryEntry root = this.GetDirectoryEntry("IIS://" + this.DomainName + "/W3SVC/AppPools/" + AppPoolName);

    return root;

}

/// <summary>

/// Retrieves an Adsi Node by its path. Abstracted for error handling

/// </summary>

/// <param name="Path">the ADSI path to retrieve: IIS://localhost/w3svc/root</param>

/// <returns>node or null</returns>

private DirectoryEntry GetDirectoryEntry(string Path)

{

    DirectoryEntry root = null;

    try

    {

        root = new DirectoryEntry(Path);

    }

    catch

    {

        this.SetError("Couldn't access node");

        return null;

    }

    if (root == null)

    {

        this.SetError("Couldn't access node");

        return null;

    }

    return root;

}

AppPools are stored under:

IIS://localhost/W3SVC/AppPools

And you can access a specific pool through the Children collection. For ADSI paths a child looks like this:

IIS://localhost/W3SVC/AppPools/DefaultAppPool

From there you get a DirectoryEntry object and you can fire away on the properties of the pool and set thing like the impersonating account and various health checks. I didn’t need to look closely at this but I couldn’t find the MSDN documentation on IIsApplicationPool that shows the member properties. The MSDN documentation for IIS’s ADSI support (and even the IIS6 WMI support) is just plain awful and scattered through many places. If anybody happens to find a link with the member properties post it here.

Once you have an Application Pool it can be attached to a virtual directory/Application via its AppPoolId:

DirectoryEntry VDir = new DirectoryEntry("IIS://localhost/W3SVC/ROOT/WebStore");

VDir.Properties["AppPoolId"].Value = this.ApplicationPool;

VDir.CommitChanges();

And there you have it. I’ve updated the Web Configuration Utility online and it includes the AppPool configuration code, and a recent update to the West Wind Web Store also includes this code as part of the configuration.